1. Field of the Invention
This invention relates to an injector for the injection of samples to be analyzed in a gas chromatographic capillary column and, more precisely, to an injector of the non vaporizing direct on-column type, comprising an accessory device applicable thereof to allow its use also to perform injections of the vaporizing type with undilutable samples or concentrated solutions requiring a splitting of the vaporized sample, as well as to eliminate the solvent before the sample is transferred to the capillary column.
2. Description of the Prior Art
In U.S. Pat. No. 4,269,608 assigned to the same assignee, there is described an injector which can perform the injection of samples to be analyzed without vaporization, directly in the gas chromatographic column.
Said injector comprises a duct for the introduction of the injection syringe needle which can be closed by means of a valve, the lower section of said duct housing the end of a gas chromatographic column.
Said gas chromatographic column end is pneumatically connected to the duct thanks to an O-ring kept in position by a small tube coaxial to the column and screwed to the injector body. This small tube, according to what is described and claimed in the aforementioned patent, forms a jacket around the column head and the hollow space between the jacket and the column is fed with a fluid at a controlled temperature.
From U.S. Pat. No. 4,383,839 there is also known a method for the injection with vaporization of a liquid sample in a gas chromatographic capillary column comprising the steps of
(a) injecting the liquid sample into the initial part of a sample vaporization tube which does not contain a stationary liquid phase (or contains an immobilized phase), the sample being kept liquid during the whole injection process; PA0 (b) heating the vaporization tube and feeding it with carrier gas to entrain the vaporized sample; PA0 (c) diverting part of the resulting mixture of vaporized sample and carrier gas by means of a splitter and sending the remaining part to a gas chromatographic column containing a stationary liquid phase for chromatographic separation.
The vaporization tube can be empty or a fiberglass sponge can be placed in it to hold the sample when it is in the liquid state and to release it when it passes to the vapour state. In fact, the fiberglass sponge is impermeable to the sample at the liquid state, while it is permeable to the sample when the letter is at the vapour state.